1 Department of Internal Medicine, Dow Medical College, Karachi, Pakistan.
2 Department of Internal Medicine, University of Arizona, Tucson, AZ, USA.
3 Department of Cardiology, Stony Brook School of Medicine, Stony Brook, NY, USA.
4 Department of Medicine (Cardiovascular Division) and Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA.
5 Department of Radiology. Vancouver General Hospital, 899 12thAvenue W, Vancouver, British Columbia, Canada.